Production of alpha-chloracrylic acid esters



Unite PRODUCTION OF ALPHA-CIEORACRYLIC ACID ESTERS Manfred Minsinger, Ludwigshafen (Rhine), and Herbert Friederich, Worms, Germany, assignors' to Badische Anilin- & Soda-Fabrik Aktiengesellscliaft, Ludwigshafen e), Germany N Drawing. Filed Feb. 28, 1957, Ser. No. 642,935

Claims priority, application Germany Mar. 1, 1956 12 Claims. (Cl. 260-486.)

This invention relates'to a process for the production of alpha-chloracrylic acid esters by the catalytic splitting ofi of hydrogen chloride from dichlorpropionic acid esters which contain at least one chlorine atom in alphaposition.

It is known to prepare monomeric alpha-chloracrylic acid esters by splitting off hydrogen chloride from the "esters of dichlorpropionic acids, such as alpha.alpha- .dichlorpropionic acid or alpha.beta-dichlorpropionic acid.

chloride is thereby split oh by stoichiometrical amounts of basic-reacting substances.

According to older proposals, alpha-chloracrylic acid esters can also be prepared by a catalytic process in 'which the'vapors of alpha.beta-dichlorpropionic acid StatesrPatent O7 esters are led at elevated temperatures in the gas phase over catalysts, which consist of metal salts which are applied to carrier substances such as carbon and the like.

We have now f'ound'that alpha-chloracrylic acid esters "can be prepared in a simple'way'from dichlorpropionic acid esters which contain at least one chlorineatom in alpha-position, by treating these dichlorpropionic acid esters with catalytic amounts of organic compoundsfrom the group consisting of acid amides,.acid.imides, acid acid amides. Cyclic acid amides (lactams) containing from 5 to 9 ringmembers which may be substituted on the N-atom are also effective catalysts, for example pyrrolidone-2, N-methylpyrrolidone-Z, e-c'aprolactarri, wcaprylic lactam and the like. Suitable acid imides derive from aliphatic or aromatic dicarboxylic acids, such as succinimide or phthaliinide.

, Other substances eflfective as catalysts are for example the nitriles of saturated aliphatic monoor dicarboxylic acids containing not more than 8 carbon atoms, and the'monoor dinitriles of aromatic monoor dicarboxylic acids, for example acetonitrile, succinic acid dinitrile,

adipodinitrile,'phthalodinitrile and the like.

Amines catalysts which can be used are for instance Patented Sept. 27., 196.0

aliphatic or aromatic,'primary, secondary or tertiary monoor diamines, such as N-methylaniline, N.N-dimethylaniline, quinoline, isoquinoline, ortho-chloraniline, meta-chloraniline, para-chloraniline, N-butylpyrrolidine, N-alkylpiperidines, alkylpyrid-ines, N.N-dibutylaminoethanol, NzN-diethylan'iinopropanol, N.N-dimethylaminopropanol and phenothiazine.

The amines used in catalytic amounts may contain, besides the amino group, other functional groups,.such as OH-groups, halogen, carbonyl or carboxyl groups, or also sulfur in combined form.

Those amines of which the boiling point is-similar to or higher than that of the alpha-chloracrylic acid ester formed have proved especially suitable catalysts for the splitting oil of hydrogen chloride. It is preferable to Work while excluding water.

Carboxylic or sulfonic acids may also be used as catalysts, preferably the saturated aliphatic mono-, dior polycarboxylic acids with a chain length of from 2 to 8 carbon atoms, for example propionic acid, normal butyric acid, isobutyric acid, pentane acids, hexane acids, heptane acids and C -fatty acids, for example 2-ethylhexane-acidl or dicarboxylic acids, such as succinic acid, glutaric acid or adipic acid. Halogenated aliphatic carboxylic acids are also especially suitable, as for example monochloracetic acid, dichloracetic acid, trichloracetic acid, alpha-chlorpropionic acid, beta-chlorpropionic acid, alpha.beta-dichlorpropionic acid, alpha.alpha-dichlorpropionic acid, alpha.alphabeta trichlorpropionic acid, alpha-chlor-normal-butyric acid, beta-chlori'sobutyric acid and the like.

Aromatic carboxylic acids, such as benzoic acid, salicyclic acid and ortho -chlorbenzoic acid, arealso effective. Among the sulfonic acids, the aromatic sulfonic acids .are especially suitable, such as para-toluenesulfonic acid, ortho-toluenesulfonic acid and para-nitrotoluene-ortho- 'sulfonic acid. "These catalytically activesubstances are preferably used in amounts of 0.1 to 10% with reference tothe weight of dichlorpropionic acid ester. They can be used in'pure form or in admixture with each other, or also in the form of their hydrohalides' in sofar as theyare :capable of'forming the same.

The splitting ofi of'hydro'gen chloride-may beefiected either in the liquid or gas phase.

When workin-gin theg'as phase, the catalystused is supplied-in vapor form to the reaction vessel, preferably together with the dichlorpropionic acid ester.

nitriles and the amines, or with carboxylic or sulfonic i The reaction'may becafliedout for example by mutually vaporizing the dic'hlorpropioni'c' 'acid'- ester and the catalyst and leading them in the'gas phase, preferably after dilution with indifferentgases, such as nitrogen or carbon monoxide, through the reaction vessel. The reaction vessel' can be filled with filler bodies, iorexample of glassw In general it is preferable to Work at temperatures 'between 200 and 550 C., preferably between about'22i) and 350 C. The most favorable working temperature is diflierent for the individual catalysts and initial esters and can readily be ascertained by preliminary-experiment. 1

The process can be carried out at normal, reduced or also moderately increased pressure discontinuously or continuously. Thealpha-chloracrylic acid esters a re'obtained in good yields. withoutany appreciable polymerization taking place; the unconverted alphabeta-dichlorpropionic acid ester is again led through the'reaction'vessel after theaddition of catalyst; r

When working in the liquid phase, the temperature may be lowered considerably as compared'withworking in the gas phase; the splitting off of hydrogenchl'oride in this case is preferably carried out between 80 C. and the boiling point of the alpha-dichlorpropionic acid ester in question. The preferred reaction temperatures lie between 130" and 160 C. The process is preferably carried out in a reaction vessel which is resistant to corro- 'sion, for example made of stainless steel or graphite,

which is heated to the desired reaction temperature, at normal pressure or at reduced or increased pressure. It may be operated continuously in a simple manner. In order to avoid spontaneous polymerization of the chloracrylic acid ester formed, it is preferable to add a polymerization inhibitor, such as phenothiazine or hydroquinone.

The reaction products can be separated by distillation.

After distilling off the alpha-chloracrylic acid ester, the

remaining mixture of dichlorpropionic acid ester and A B O D E F I G I H I J 2 157 N.N-dimethy1formamide 160 6 90 84 88 3 157 7.5 N-methylpyrrolidone-Z. 140 6 80 22 73. 3 90 4 157 20 N -methylnyrrolidone-2- 140 6 85 40 23 74. 5 93 8 hydrochloride.

157 15 N-butyl-forrnamide 160 6 75 30 38 81 76 3 157 15 N.N-dimethylacetamide 150 6 88 40 18 74 5 98 157 15 pyrrolidone-2 150 6 80 37 23 76 5 86 157 1521 TIggt1hylpyrrolidone and. 130 6 95 27 32 83 94 2. 9 157 10 benzonitrile 150 6 45 95 15 39. 5 94 5 10 157 10 succinodinitrile 150 6 44 90 16 42. 7 68 157 10 adiponitrile 150 6 110 13 30 97 12 157 10 suceinimide 150 6 45 90 21 42. 5 87 5 1 157 3 nhthalimida 150 6 48 88 15 44 89 catalyst can agam be sub ected to the reaction, 1f de- Example 14 sired after the addition of fresh dichlorpropionic acid ester.' The unconverted dichlorpropionic acid ester may however also be recovered by distillation and then re-.

acted.

By prolonging the residence time and also by varying the reaction temperature, the reaction can however also be directed to give a quantitative conversion of the di chlorpropionic acid ester introduced.

By adding halides of metals of the 2nd to 8th groups of the periodic system, the most favorable temperature in the process can'be lowered by about 10 to 15 C. For this purpose there may be used for example complex compounds of the metal halides with the catalysts, if desired with an excess of the catalyst concerned; mixtures of different complex compounds may also be used.

i Suitable metal halides are for example the halides of zinc, cadmium, aluminium, chromium or cobalt. It is not necessary tou se isolated complex compounds of such metal halides, but on the contrary it is sufiicient to add the metal halide to the mixture of dichlorpropionic acid ester and catalyst, if desired while heating. It is recom mended to use between 0.1 and 5% of metal halide with reference to the dichlorpropionic acid ester introduced.

According to the present invention it is possible to prepare for example the methyl, ethyl, propyl, n-butyl and isobutyl esters of alpha-chloracrylic acid.

The following examples will further illustrate this invention but the invention is not restricted to these examples. The parts specified in the examples are parts by weight.

Example 1 A mixture of 157 parts of alpha.beta-dichlorpropionic acid methyl ester, 15 parts of N-methyl-pyrrolidone-Z and 1 part of phenothiazine is heated for 6 hours at 160 C. in a' vessel provided with a reflux condenser. By fractional distillation there are obtained from the reaction mixture 105 parts of alpha-chloracrylic acid methyl ester, 20 parts of alpha.beta-dichlorpropionic acid methyl ester and 26 parts of residue consisting mainly of the catalyst or its hydrochloride. With a conversion of 87%, the yield of aplha-chloracrylic acid methyl ester is 99% with reference to the alpha.beta-dichlorpropionic acid methyl ester converted.

A mixture of 157 parts of alpha.beta-dichlorpropionic acid methyl ester and 12 parts of phenothiazine is heated for 6 hours at 150 C. in a vessel provided with a reflux condenser. By fractional distillation there are obtained from the reaction mixture 74 parts of alpha-chloracrylic acid methyl ester, 59 parts of alpha.beta-dichlorpropionic acid methyl ester and 19 parts of residue which consists mainly of the catalyst or its hydrochloride and the stabilizer. With a conversion of 67% the yield of alphachloracrylic acid methyl ester is 98.5% with reference to the alphabeta-dichlorpropionic acid methyl ester converted.

' Examples 15-21 Example 15 16 17 18 19 20 21 parts of aIpha.beta-dichlorpropionic acid methyl ester 157 157 157 157 157 157 157 parts of catalyst-H part of phenothiazine as stabilizer A B O D E F G temperature, 0-- 150 150 145 150 145 140 140 time in hours 6 6 6 6 4 4 4 parts of alpha-chlor- I acrylic acid methyl ester 45 72 65 58 65 parts of unconverted alpha.beta-diehlorpropionic acid methyl ester 9o 48 44 a2 72 as 35 residue+cata1yst+stabilizer Into the top of a vertically-arranged tube of ceramic material 120 centimetres long and 40 millimetres in diameter there are led per hour the vapors of grams of alpha.beta-dichloropropionic acid methyl ester to which 75 2% by weight of -N-methylpyrrolidone-2 have been added; The reaction tube is filled with 6 millimetre glass Raschig rings and is heated externally to 320 C. .After a mixture of 2,000 grams of alpha.beta-dichlorpropionic acid methyl ester with 40 grams of N-methylpyrrolidonc- 2 as catalyst has been. led through, 1,938 grams of a reaction mixture are obtained which is fractionallv distilled.

There are obtained 328 grams of alpha-chloracrylic acidmethyl ester and also 1,552 grams of alpha.betadichlorpropionic acid methyl ester. The distillation residue amounts to 52 grams and consists mainly of the hydrochloride of the catalyst. The yield of alpha-chloracrylic acid methyl ester amounts to 96% of the theoretical yield with reference to the alphabeta-dichlor- .propionic acid methyl ester converted.

Example 23 The procedure of Example 22 is followed with the following differences.

2,000 parts of alpha.beta-dichlorpropionic acid methyl ester are usedat therate of 100 parts per hour with 50 parts of N.N-dibutylformamide, the temperature being 300 C. 'Thereare obtained 348 parts of alphachlo'racrylic acid methyl ester, 1,521 parts of alpha.betadichlorpropionic acid methyl ester and 64 parts of residue. Yield 95% of the theoretical.

Example 24 Following the procedure of Example 2.2 with 2,000 parts of alphabeta-diehlorp-ropionic acid methyl ester at therate of 100 parts per hour with 50 parts of adipodinitrile at 340 C., there are obtained 315 parts of alpha-chloracrylic acid methyl ester, 1,560 parts of alpha. beta-dichlorpropionic acid methyl ester and 70 parts of residue. Yield 93% of the theoretical.

Example 25 Following the procedure of Example 22 with 2,000

dichlorpropionic acid methyl ester and .SIpartsofreSidne. Yield 93% of'the theoretical.

Example 27 Example 28 A mixture of 157 parts of alpha.beta-dichlorpropionic acid methyl ester, 8 parts of 2-ethylhexane acid-1 and 0.5 part of picric acid is heated for 6 hours at 145 C. in a vessel provided with a reflux condenser. By fractional distillation there are obtained from the reaction mixture 52 parts of alpha-chloracrylic acid methyl ester, 86 parts of alpha.beta-dichlorpropionic acid methyl ester and 13 parts of products of higher boiling'point (residue) consisting mainly of the catalyst and the stabilizer used. With a'conversion of the yield of alpha-chloracrylic acid methyl ester is 95.5% with reference to the alpha. beta-dichlorpropionic acid methyl ester converted.

Examples 29-44 These examples are carried out in a similar way to Example 28 and the following table shows the initial materials, the catalysts, stabilizers, temperatures, time of reaction, the products, the percentage of the conversion and of the yields.

parts of unparts of alpha. parts of catalyst+0.5 p s o converted es e-lco er- Example beta-dichlorpart of pieric acid as Temper- Time in alpha-chloralpha.betacatalyst+ sion, yield,

propionic acid stabilizer ature hours acrylic acid dichlor-prostabilizer percent percent methyl ester methyl ester pionic acid methyl ester 157 8 monoehloracetic acid. 140 6 54 81 14 48 93 157 8 dichloracetic acid 140 6 54 83 13 47 96 157 8 trichloracetic acid 140 6 75 12 51 96 167 8 alphaalpha-dichlor- 150 6 95 41 17 74 96 propionic acid.

157 8 alpha.beta-dlchlor- 150 6 17 58 97 propionic acid.

157 8 alpla-chlorpropionlc 145 6 61 10 52 97 157 8 betlzg-chlorproplonic 145 6 55 15 49 93 157 8 alpha-chlor-n-bu- 145 6 76 50 16 68 92 tyric acid.

157 8 beta-chlor-isobu- 145 6 55 75 18 52 87. 5

tyric acid.

157 8 para-toluene-sul- 150 6 74 44 22 72 86 phonic acid.

157 8 para-nitrotoluenc- 150 6 48 16 46 87 ortho-sulfonic acid.

157 6 benzoic acid 145 6 50 85 14 46 90. 5

157 6 salicylic acid 145 6 57 75 12 52 90. 5

157 6 ortlo-chlorbenzolc 145 6 42 11 40 88 aci 158 5 succinic acid 150 6 43 95 11 40 90 157 6 adipic acid 150 6 64 71 10 55 97 parts of alpha.beta-dichlorpropionic acid methyl ester at the rate of 100 parts per hour with 50 parts of benzonitrile at 340 C., there are obtained 384 parts of alphaacrylic acid methyl ester, 1,370 parts of alpha.beta-didichlorpropionic acid methyl ester and 81 parts of residue. Yield 90% of the theoretical.

Example 26 Following the procedure of Example 22 with 2,000 parts of alpha.beta-dichlorpropionic acid methyl ester at the rate of 100 parts per hour with 60 parts of pyridine at 330 C., there are obtained 475 parts of alphachloracrylic acid methyl ester, 1,338 parts of alpha.beta- 75 amides containing from 1 to 4 carbon atoms, cyclic acid amides containing from 5 to 9 ring members, carboxylic acid imides of aliphatic dicarboxylic acids, carboxylic acid with a chain length from 2 to 8 carbon atoms.

2. A process as claimed in claim 1 wherein the catalytic splitting ofi of hydrogen chloride is carried out in the liquid phase at temperatures between 80 C. and the boiling point of the alpha,beta-dichloropropionic acid ester.

3. A process as claimed in claim 1 wherein the catalytic splitting off of hydrogen chloride is carried out in thegas phase at temperatures between 200 and 550 C.

4. A process as claimed in claim 3 wherein the catalytic splitting off of hydrogen chloride is carried out in the gas phase at temperatures between 220 and 350 C. 5. 'A process as claimed in claim 1 wherein in addition to the'said catalyst there is also added 0.1 to 5 percent of a halide of a member of the group consisting ofzinc, cadmium, aluminum, chromium and cobalt.

6. A process as claimed in claim 1 wherein the process is carried out under anhydrous conditions. I

7. A process for the production of an ester of alphachloracrylic acid which comprises catalytically splitting off hydrogen chloride from a lower alkyl ester of alpha,betadichloropropionic acid in the presence, as catalyst, of 0.1 to 10% with reference to the weight of the alpha,beta-dichloropropionic acid ester of an anime of which the boiling point is higher than that of the alpha-chloracrylic acid ester formed.

8. A process as claimed in claim 7, wherein the catalyst used is quinoline;

9. A process asclaimed in claim 7, wherein the catalyst used is isoquinoline.

10. A process as claimed in claim 1, wherein the catalyst used in adipodinitrile.

11. A process for the production of an ester of alphachloracrylic acid which comprises catalytically splitting off hydrogen chloride from a lower alkyl ester of alpha, beta-dichloropropionic acid in the presence as a catalyst of 0.1% to 10% by weight based on the weight of the alpha,beta-dichloropropionic acid ester of .Nmethylpyrrolidone.

12. A process for the production of an ester of alphachloracrylic acid which comprises catalytically splitting ofi hydrogen chloride from a lower alkyl ester of alpha, beta-dichloropropionic acid in the presence as acatalyst of 0.1% to 10% by weight based on, the weightjof the alpha-beta-dichloropropionic acid ester of'N-butyl pyrrolidineQ i i I References Cited in the file of this patent, UNITED STATES PATENTS Pollack Decf2, 195 s UNITED STATES PATENT OFFICE CERTIICATION 0F CORRECTION Patent No. 2 954 398 September- 27 1960 Manfred Minsinger et al0 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 50, for "to-u se" read to use column 7, line 81, for "anime" read amine Signed and sealed this 23rd day of May 1961 (SEAL) Attest:

H ERNEST SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. A PROCESS FOR THE PRODUCTION OF ALPHA-CHLOROACRYLIC ACID ESTERS OF LOWER ALKYL ALCOHOLS BY CATALYTIC SPLITTING OFF OF HYDROGEN CHLORIDE AT ELEVATED TEMPERATURE FROM ALPHA, BETA-DICHLOROPROPIONIC ACID ESTERS OF LOWER ALKANOLS WHICH COMPRISES CARRYING OUT THE PROCESS IN THE PRESENCE OF 0.1 TO 10 PERCENT, WITH REFERENCE TO THE WEIGHT OF TH ALPHA, BETA-DICHLOROPROPIONIC ACID ESTER, OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF SATURATED CARBOXYLIC ACID AMIDES CONTAINING FROM 1 TO 4 CARBON ATOMS, CYCLIC ACID AMIDES CONTAINING FROM 5 TO 9 RING MEMBERS, CARBOXYLIC ACID IMIDES OF ALIPHATIC DICARBOXYLIC ACIDS, CARBOXYLIC ACID IMIDES OF AROMATIC DICARBOXYLIC ACIDS, CARBOXYLIC ACID NITRILES OF SATURATED ALIPHATIC CARBOXYLIC ACIDS CONTAINING NOT MORE THAN 8 CARBON ATOMS, MONO- AND DINITRILES OF AROMATIC MONO- AND DICARBOXYLIC ACIDS, PRIMARY, SECONDARY AND TERTIARY ALIPHATIC AND AROMATIC MONO- AND DIAMINES AND SATURATED MONO-, DI- AND POLYCARBOXYLIC ACIDS WITH A CHAIN LENGTH FROM 2 TO 8 CARBON ATOMS. 